CODA callback mechanism

Hi everyone,

     Is there any documentation that specifies the various source files 
and functions that implement CODA's callback mechanism for client 
caching?  I'm trying to modify the server so that it invalidates 
callbacks based on client-provided conditions.  For example, A opens 
file f read-only, passing the server a condition that says, "Don't 
invalidate my callback unless f has undergone 3 version changes."  Then, 
B opens file f read-write, makes a modification, and closes f. 
Normally, A would receive a callback invalidation from the server, but 
in my modified version, the server would fail to do so because f has 
only changed versions once since A registered interest.  I'm new to 
CODA, and I just recently started sifting through its massive code base. 
  If anyone could help narrow my search, I would really appreciate it. 
I'm currently planning to implement this on linux-2.4.  Thanks in advance.

-Steve